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HUMAN AND BOVINE TUBERCULOSIS.
By Dr. M. P. RAVENEL, BACTERIOLOGIST OF THE STATE LIVE STOCK SANITARY
BOARD OF PENNSYLVANIA, PHILADELPHIA, PA.
The past decade has seen the awakening of a widespread interest in the study of tuberculosis, the spirit of Oriental fatalism which has for so long led us to view with equanimity the awful loss of life annually inflicted by this great white plague having given way to an active campaign against its ravages, a campaign so far largely one of eduction, in which we strive to spread far and wide the fundamental fact that tuberculosis is a communicable disease, and from that fact, preventable. If preventable, why not prevented? With these precepts firmly implanted in the minds of the medical profession, as well as of the general public, we have reason to hope that each year will see a more careful study of the methods by which tuberculosis is spread and the means to be adopted for its prevention. On every hand societies for the prevention of tuberculosis are being formed whose object is to teach the truth concerning the disease and to dispel those false notions, chief among which may be mentioned belief in the hereditary character of tuberculosis, which in the past have led us to regard the tribute of human life as inevitable.
The intelligent prophylaxis against any disease demands a thorough understanding of the methods by which it is spread. The whole world is in accord in assigning the chief rôle in the propagation of tuberculosis to the inhalation of particles of sputum thrown off by phthisical persons, the majority of the profession agreeing with Cornet in the belief that sputum is most dangerous' when dried and pulverized, while others follow Flugge in regarding the moist floating particles thrown out during coughing, sneezing, etc., as most to de dreaded. The danger to mankind from tuberculosis of cattle has been discussed at a length and with a fervor not surpassed in the history of modern medicine. The immense practical importance of the subject to the medical profession, to those charged with making and enforcing laws for the preservation of the health of the community, no less than to every man, woman and child, justifies our deepest interest and most earnest studies.
The relation that exists between human and bovine tuberculosis, and the part played by cattle in spreading the disease among mankind, is now the great question to which attention has been drawn with renewed activity by the attitude of Professor Koch, announced in his paper before the British Congress on Tuberculosis, in July, 1901. This paper was the more striking, iv that it contained statements diametrically opposed to the former teaching of Koch that “bovine tuberculosis is identical with human tuberculosis, and is thus a disease transmissible to man.” This belief was the outcome of the experiments made by Koch at the time of his discovery of the tubercle bacillus, and has been generally accepted by the medical and veterinary professions up to the present time. So much has been written of late on the
subject that I will pass over minor differences of opinion and at once take up the consideration of the two main propositions which were formulated by Koch, and which include all points of controversy in the discussion of the relation between human and bovine tuberculosis.
Human tuberculosis differs from bovine and cannot be transmitted to cattle.
2. Though the important question whether man is susceptible to bovine tuberculosis at all is not yet absolutely decided, and will not admit of absolute decision to-day or to-morrow, one is nevertheless already at liberty to say that if such a susceptibility really exists the infection of human beings is but a very rare occurrence. I should estimate the extent of infection by the milk and flesh of tuberculous cattle, and the butter made from this milk, is hardly greater than that of hereditary transmission, and therefore do not deem it advisable to take any measures against it.
The first of these propositions is susceptible of direct experimental investigation, and can therefore be answered positively without going into the domain of theory. Professor Koch based this statement on the result of an insufficient number of experiments done by Professor Shutz and himself. A number of young cattle proved to be free from tuberculosis by the tuberculin test were infected in various ways with the bacilli of human origin or with tubercular sputum. “In some cases the tubercle bacilli or the sputum were injected under the skin, in others into the peritoneal cavity, in still others into the jugular vein. Six animals were fed with tubercular sputum almost daily for seven or eight months; four repeatedly inhaled great quantities of bacilli, which were distributed in water and scattered with it in the form of spray. None of these cattle, there were thirteen of them, showed any symptoms of disease, and they gained considerably in weight.” After six to eight months they were killed and no trace of disease was found in the internal organs. Where the injections were made small foci of suppuration had formed in which there were found a few bacilli.
Inoculations of a similar nature with bacilli from the lungs of an animal with bovine tuberculosis resulted always in rapid illness, ending often in death, while some were killed in a miserably sick condition after three months. In all cases there was extensive tuberculosis, involving the internal organs, especially the lungs and spleen.
A similar difference in pathogenic power was found in feeding experiments on pigs, where one lot of six received human tubercular sputum, and a second lot of six were given pure cultures of the bovine tubercle bacillus : and also in experiments on asses, sheep and goats, where the inoculations were made with pure cultures of human and bovine bacilli into the circulation.
Results similar to these in the main have been obtained by Smith, Frothingtham, Dinwiddie and at the laboratory of the State Live-stock Sanitary Board of Pennsylvania, and we may admit that, as a rule, cattle show a high degree of resistance to the human tubercle bacillus, and that for all experimental animals the bovine bacillus has a pathogenic power equal to the hu